The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to perform deposition of film on a substrate. Substrate processing systems typically include a processing chamber with a reaction volume. A substrate support such as a pedestal, a chuck, a plate, etc. is arranged in the processing chamber. A substrate such as a semiconductor wafer may be arranged on the substrate support.
In some applications, the film is deposited using plasma-enhanced chemical vapor deposition (PECVD) or plasma-enhanced atomic layer deposition (PEALD). During PEALD, one or more PEALD cycles are performed to deposit film on the substrate. Each PEALD cycle typically includes precursor dose, dose purge, RF plasma dose, and RF purge steps.
During deposition, process gas may be delivered to the processing chamber using a showerhead. During RF plasma dosing, RF power is supplied to the showerhead and the substrate support is grounded (or vice versa). During PEALD, plasma-enhanced conversion of the precursor occurs on the substrate.
During the dose purge and RF purge steps, inert gas such as argon is supplied through the showerhead. In addition, a secondary purge may be performed above the showerhead during some or all of the PEALD steps to prevent undesirable deposition in remote areas such as a backside of the showerhead, a top plate of the processing chamber and/or walls of the processing chamber.
When argon is used as the secondary purge gas for some nitrogen-free applications such as double-patterning, parasitic plasma may occur behind the showerhead. The power that is consumed by the parasitic plasma can be as much as 40% of the total plasma power delivered to the processing chamber. On-substrate delivered power loss usually results in looser film with elevated etch rate. The parasitic plasma induced power loss is usually non-uniform across the showerhead. More particularly, higher power loss occurs at an edge portion of the showerhead as compared to center portions of showerhead due to the RF power supplied at a stem portion of the showerhead.
The film deposited at the center of the substrate is denser than that at the edge of the substrate. As a result, the film has an edge-thick profile and high within-substrate non-uniformity, which is unfavorable for critical dimension (CD) uniformity control in double-patterning applications. In addition, operating the substrate processing system with high parasitic plasma tends to cause long term issues with wafer-to-wafer repeatability, tool drift, process defect performance, and erosion of showerhead components.